The field of the disclosure relates generally to railway cars and related components, and more particularly to a covered hopper railcar for carrying flowable materials including solid and semi-solid materials, and a method of manufacturing and operating the same.
Railway cars have been used for many years to transport a wide variety of materials. For example, covered hopper railcars transport solid flowable materials such as, for example, plastic pellets. Many known covered hopper railcars include roof hatches, bottom outlets with outlet gates, and multiple internally partitioned hoppers to facilitate gravity loading and gravity unloading of the solid flowable materials. Each hopper of the multiple hoppers included within a known railcar typically has one bottom outlet. However some known covered, multiple-hopper railcars use a gravity pneumatic outlet designed for transport of granular products such as, for example, plastic pellets from each hopper to a remote storage bin. The gravity pneumatic outlet is typically coupled to a pneumatic conveying system found at the unloading site. Gravity causes the pellets inside the hopper to flow into the outlet's product tube. A pneumatic conveying system then conveys the plastic pellets into storage silos, hoppers, or other containment devices, using a dilute phase type system that suspends the pellets in an air stream by using high-velocity and low-pressure air.
The configuration of each hopper (e.g., the size, shape, and angle to the outlets) within a covered hopper railcar is controlled by the product's angle of slide (i.e., the angle required to get the product to flow to the outlet gate under the action of gravity alone). However, unlike a gravity-only discharge outlet, the product in a multiple hopper railcar is not unloaded directly under the hopper. Rather, it is pneumatically conveyed laterally to a silo or process bin. Hence unloading a conventional covered hopper car with gravity pneumatic outlet gates necessitates coupling and uncoupling the unloading system to and from each hopper individually. This coupling and uncoupling is time consuming and labor intensive, thereby increasing the costs of unloading.
Moreover, to meet the angle of slide to the outlet, the hoppers must diverge longitudinally, which creates a saw-tooth shape when viewed from the side of the railcar. The saw-tooth configuration is the consequence of the hopper slopes needed to get the product to slide toward the outlet. Unusable interior space is formed by the diverging slopes of adjacent hoppers. The hopper saw-tooth shape also reduces the usable volume. This lost space translates into the requirement for a longer car to hold an equivalent volume or payload. A longer car increases the difficulty in transit of negotiating curves. A plurality of longer railcars increases the overall length of the train, thereby limiting the number of cars in certain trains that are limited by overall train length.
The saw-tooth shape also reduces the effectiveness of the car body and its hoppers from transmitting car-to-car train action loads. Consequently, these known railcars require a more substantial structural member (i.e., either a center sill or a side sill) to transmit train action longitudinal loads. Furthermore, railcar body bending loads are less efficiently carried by the saw-tooth design of the hoppers, because the effective bending section is limited to the height of the side sheet, rather than the entire depth of the car body.